Zeng, Weiqing , Li, Yonghua , He, Sheng-Yang .
Identification and characterization of the Arabidopsis mutant scd2 (Susceptible to Coronatine-Deficient Pseudomonas syringae pv. tomato strain DC3118).
Our group recently found that stomatal closure is involved in bacterium-induced innate immunity in Arabidopsis. Arabidopsis stomata actively close in response to the plant and human pathogenic bacteria, including Pseudomonas syringae pv. tomato (Pst) DC3000. In addition, PAMPs derived from bacteria, such as flagellin and lipopolysaccharides (LPS), also induce stomata closure. This stomata-based defense, however, could be overcome by coronatine, a phytotoxin virulence factor produced by Pst DC3000. A coronatine synthesis-defective mutant, Pst DC3118, is unable to inhibit stomatal closure and therefore does not efficiently enter Arabidopsis leaves through stomata to cause disease. However, Pst DC3118 is as virulent as the wild-type DC3000 when infiltrated into Arabidopsis leaves, bypassing the stomatal defense.
To identify the components involved in bacterium/PAMP-induced stomatal closure, a genetic screening was designed by taking advantage of the fact that the coronatine-deficient Pst DC3118 does not induce disease symptoms when applied on the leaf surface. An Arabidopsis T-DNA insertion population was screened for mutants that allowed Pst DC3118 to cause disease symptoms. One of the mutants identified is scd2. The stomata of this mutant plant showed only a partial response to ABA or flagellin22. Currently the scd2 mutant is being analyzed for its basal resistance, gene for gene resistance, and HR responses.
In addition, we found that the wax composition of scd2 leaves showed 80% decrease in alkane and two-fold increase in aldehyde. On the other hand, the wax composition in scd2 stems remains similar to wild type plants. These results suggest that the scd2 mutant is affected in leaf-specific wax biosynthesis. Currently we are cloning the gene through physical mapping. Identification of the gene should improve our understanding of the connection between the leaf surface structure and plant defense against bacteria pathogens.
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1 - Michigan State University, DOE-Plant Research Laboratory, Rm 222, Plant Biology Building, East Lansing, MI, 48823, USA
2 - Michigan State University, Department of Plant Biology
3 - Michigan State University, DOE-Plant Research Laboratory
Presentation Type: Plant Biology Abstract
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM